Adder’s-tongue

How to recognise it

Growth form

Small perennial fern of 5–25 cm, usually with one leaf per plant; often grows in small groups or large colonies.

Leaf

A single oval to broadly lance-shaped, untoothed leaf of 3–12 cm, fleshy and glossy pale green, with a fine network of veins; at its base it wraps around the spore stalk.

Spores

An upright stalk with a narrow, pointed spore spike of 2–5 cm, with two rows of sunken spore cases; ripe in June–July.

Roots

A short, upright rhizome with fleshy roots, from which new plants can sprout; it lives in partnership with soil fungi.

Season

The leaf appears in April–May and disappears again in July–August; for the rest of the year there is nothing to see.

Confusion with

Moonwort has a divided leaf with half-moon-shaped leaflets and a branched spore cluster. Young leaves of orchids or plantains have parallel veins and no spore spike.

Pruning: August–September

Why grow it?

• A sign of old grassland: where adder’s-tongue grows, the ground has not been fertilised, reseeded or ploughed for a long time.
• A botanical surprise: a fern that looks nothing like a fern, with a net-veined leaf and a spore spike like a tongue.
• It belongs to species-rich, unimproved grasslands and wet dune slacks, often together with orchids, yellow rattle and other special plants.
• A reward for patient, late mowing in a wildlife garden or an old lawn.
• It belongs to an old, separate branch of the ferns, with a structure and way of life all of its own.

Adder’s-tongue: where does it grow best?

• In the wild: old, unimproved hay meadows and pastures, wet dune slacks, damp heath and heath edges, verges, clearings in open woodland and sometimes old lawns and churchyards.
• Moist to wet, nutrient-poor soil, from acid to chalky; often where the water table is high in winter.
• Sun to light partial shade, in short or sparse grass.
• In the garden: an old lawn that has never been fed, or a poor wildflower meadow that is mown late.

Goes well with

• Greater yellow rattle: A semi-parasite that holds back the grass, so small plants such as adder’s-tongue get more light.
• Cuckooflower: Lilac flowers in April–May in the same moist grassland.
• Ragged-Robin: Pink, ragged flowers in May–June in a moist, unimproved hay meadow.
• Sweet vernal grass: A fine, early-flowering grass of unimproved grassland that leaves room for small plants.

Adder’s-tongue: when and how to plant it?

1. Adder’s-tongue is rare and vulnerable: never dig it up from the wild and do not pick it.
2. It is rarely sold. Buy it only from a specialist nursery for ferns or native plants.
3. Plant in April, as soon as the leaf appears, in moist, nutrient-poor soil with short grass; set the plant at the same depth as in the pot.
4. To move it within your own garden, lift a large turf of 30 by 30 cm with all the soil around it, so the roots and the soil fungi move with it.
5. Do not feed, and water only during a long dry spell in the first spring.
6. Better still: from now on, mow an old lawn or hay meadow late. Adder’s-tongue often turns up by itself, or an existing group spreads.

Care

Mowing

Do not mow between April and the end of July, so the leaf can ripen its spores. Then mow in August–September and remove the cuttings.

Feeding

Never: manure, compost and fertiliser make the grass grow fast and crowd out adder’s-tongue.

Water

Not needed in suitable, moist soil. A dry summer does no harm: by then the leaf has already gone.

Marking

In May, put a few sticks by the group so you can find the spot again and do not mow over it.

Soil

Do not dig, rotavate or scarify the spot: this spares the roots and the soil fungi.

Tip: Mow a patch of old lawn or hay meadow only from August and search on your knees in May: adder’s-tongue often grows unnoticed in the grass for years.

Pruning and mowing

Pruning months: August–September.

When: No pruning. Mow the grassland only in August–September, when the leaf has withered.

How:

• Mow only when the leaf and spore spike have turned yellow or disappeared, usually from August.
• Then mow short and remove the cuttings, so the soil stays poor.
• In a lawn: spare the spot from April to the end of July and mow around it.

Caution: Mowing too early costs the plant that year’s spores; mowing too early every year weakens the colony.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Root buds

New little plants sprout from the roots by themselves; this is how it slowly forms a colony. Within your own garden you can move a turf in April.

Spores

Almost impossible at home: the spores germinate underground into a tiny plant without chlorophyll, which depends on soil fungi for years.

Adder’s-tongue: how does it get through the winter?

Hardy to −30 °C.

• The leaf disappears as early as summer; the plant overwinters underground as a short rhizome with fleshy roots.
• Fully hardy, to about −30 °C.
• Wet winters with a high water table suit it well.
• The number of leaves can vary greatly from year to year; a year without leaves does not mean it has gone.

Diseases and pests

• Mowing too early: The leaf is cut before the spores are ripe. Spare the spot from April to the end of July.
• Fertilising: The grass grows too tall and dense. Stop feeding and always remove the cuttings.
• Drying out: When the water table drops, it declines. Do not install drainage and let rainwater soak into the garden.
• Hard to find: Among the grass you can barely see it. Search on your knees in May and mark the group with sticks.

Through the year

• April: The first leaves appear. Mark the spot, do not mow.
• May: Leaf fully grown; the spore spikes rise above the leaf.
• June: The spores ripen. Do not mow yet.
• July: Leaf and spore spike turn yellow and disappear.
• August: Mow the hay meadow or lawn patch and remove the cuttings.
• September: Mow again if needed; remove the cuttings.
• December: Resting underground. Do not feed.

Did you know?

• The scientific name comes from the Greek ophis (snake) and glossa (tongue): the spore spike sticks out of the leaf like a snake’s tongue.
• A tropical relative, Ophioglossum reticulatum, has one of the highest chromosome numbers ever counted in a living thing: more than 1200.
• The spores first grow into a tiny underground plant without chlorophyll, which lives with soil fungi for years before a first leaf appears above ground.